1. Field
Aspects of embodiments of the present invention relate to a display device. More particularly, aspects of embodiments of the present invention relate to a digital driving type of display device.
2. Description of the Related Art
Recently, display devices such as a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting display have been commercially available.
A display device includes a display panel formed of a plurality of pixels arranged in a matrix format. A display panel includes a plurality of scan lines formed in a row direction and a plurality of data lines formed in a column line, and the plurality of scan lines and the plurality of data lines are arranged to cross each other. Each of the plurality of pixels is driven by a scan signal and a data signal respectively transmitted from a corresponding scan line and data line.
The display device is classified into a passive matrix type of light emitting display device and an active matrix type of light emitting display device depending on the method of driving the pixels. In view of resolution, contrast, and response time, the trend is towards the active matrix type where the respective unit pixels are selectively turned on or off.
The active matrix type of light emitting display device is generally applied with an analog driving method or a digital driving method. While the analog driving method is a method of expressing a grayscale level as a level of the data voltage, the digital driving method is a method of expressing the grayscale level by a time or a number of times that the data voltage is applied while a data voltage level is constantly maintained.
It is usual in an analog driving scheme to install a compensation circuit for compensating a dispersion characteristic of a threshold voltage of a driving transistor for controlling a current amount of a driving current flowing to a light-emitting device in a pixel. The analog driving scheme reduces a time that is allocated when a data signal is applied to each pixel as a resolution of the display device is increased. Accordingly, a voltage range of the data signal is reduced and the display device becomes more sensitive to a process variation of the driving transistor.
On the contrary, the digital driving scheme is not as sensitive to the process variation of the driving transistor since the data signal has an on-off voltage.
However, the digital driving scheme has a greater number of times of charging and discharging the data line and also has a greater voltage range of the data signal compared to the analog driving scheme. Accordingly, the digital driving scheme has very high power consumption compared to the analog driving scheme. For example, a voltage difference between a minimum voltage of the data signal and a maximum voltage is 3 V according to the analog driving scheme, while the voltage difference between the minimum voltage and the maximum voltage is 10 V according to the digital driving scheme. The digital driving scheme has eight to ten times the number of charges and discharges of the data line compared to the analog driving scheme. By the difference, the digital driving scheme has about 90 times the power consumption for driving compared to the analog driving scheme.
Further, the digital driving scheme requires about ⅛- 1/10 the time for inputting the data signal into respective pixels compared to the analog driving scheme, thereby lacking a time margin for inputting the data signal. To overcome the insufficiency of the time margin, a method for reducing wire resistance by increasing wiring thicknesses of the data line and the scan line is used to reduce a delay caused by the wire.
However, there is a limit in the process in the case of increasing the thickness of wiring, and when the thickness of wiring is increased, a time for manufacturing the display device is increased which may become a factor for reducing productivity of the display device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is known to a person of ordinary skill in the art.